AC Battery: Modular Layout and Cyber-secure Cell-level Control for Cost-Effective Transportation Electrification

Abstract

This paper proposes a three-phase AC battery based on the modular multilevel converter (MMC) and investigates the effects of cyber attacks on it. The AC battery concept allows plug and play combinatorial integration of diverse battery cells with different characteristics such as nominal voltage, state of charge (SoC), state of health (SoH), and capacity into modular and reconfigurable battery packs that can cost-effectively cover a broad range of applications from electrified vehicles to stationary storage. To this end, in each sub-module (SM) of the MMC, battery cells (or modules) are connected to its capacitor, enabling a cell-to-cell control. In this scenario, the traditional battery management system (BMS) can be replaced by control schemes for the converter aiming to equalise critical parameters associated with battery cells. Unlike previous works, the proposed battery concept considers a local controllers (LC) in each SM of the MMC, achieving a modularisation in computing capacity for the MMC control system. Under this framework, a distributed control scheme based on the consensus theory is proposed for SoC regulation among the battery cells. Also, it is shown that cyber attacks are real threats to this electrical system. In particular, this work studies the effects of the specific cyber attack named false data injection attack (FDIA) on the proposed distributed control scheme for SoC regulation.